This application claims priority under 35 U.S.C. §119(a) on Patent Application No. 2008-193928 filed in Japan on Jul. 28, 2008, the entire contents of which are herein incorporated by reference.
The present technology relates to a paper discharge apparatus that sequentially discharges paper through a discharge outlet, and stacks and stores the paper, and a post-processing apparatus and an image forming apparatus that include such a paper discharge apparatus.
This type of paper discharge apparatus is an apparatus that is applied to, for example, an image forming apparatus, such as a copy machine, or a post-processing apparatus for an image forming apparatus, and that sequentially discharges, stacks and stores a plurality of printed or post-processed paper sheets onto a discharge tray.
For example, JP 2006-248685A discloses such a paper discharge apparatus. According to this disclosure, in order to align a plurality of paper sheets on a discharge tray, the discharge tray is inclined with the outermost end side (the downstream side in the paper discharge direction) of the discharge tray upward so that each sheet of paper slides on the discharge tray and one end of the sheet abuts the rear end side of the discharge tray and is aligned.
JP H02-31266U discloses a technique in which a lower guide plate that is disposed on an inclined tray and that is biased horizontally and an upper guide plate that is disposed overlapping the lower guide plate and that is axially supported on the upper side of a paper discharge outlet are provided, and paper is discharged from the discharge outlet onto the lower guide plate and is interposed between the lower guide plate and the upper guide plate while the paper on the lower guide plate is pressed by the weight of the upper guide plate. As the number of paper sheets on the lower guide plate increases, due to the weight of the paper sheets, the lower guide plate is inclined downward against the biasing force until the lower guide plate comes into contact with the inclined tray.
JP 2003-182921A discloses a technique in which a discharge tray and an auxiliary tray that is disposed on the rear end portion (the upstream side portion in the paper discharge direction) of the discharge tray are provided, post-processing is performed on a plurality of paper sheets in a state in which the paper sheets are discharged straddling the discharge tray and the auxiliary tray and, after that, the auxiliary tray is put away so that the paper sheets are placed on the discharge tray with one end of the paper sheets abutting the rear end side of the discharge tray for alignment.
Although various attempts have been made on conventional paper discharge apparatuses so as to properly align the edges of a plurality of paper sheets, none of them addresses the straightening of curl in paper. In an image forming apparatus, paper is heated in a fixing process and, as a result, the paper is curled by that heating. At this time, not only the leading edge and trailing edge of paper are curled, but also both sides of the paper are curled. That is, four edges or corners of the sheet of paper are curled.
Conventionally, there have been no means for effectively straightening such four curled edges or corners of a sheet of paper, so reliance was placed on the phenomenon in which the paper naturally returns to its flat state on the discharge tray.
The present technology has been conceived in view of the above problems encountered with conventional technology, and it is an object of the technology to provide a paper discharge apparatus that is capable of effectively straightening four curled edges or corners of a sheet of paper, and a post-processing apparatus and an image forming apparatus that include such a paper discharge apparatus.